feat(ext): org error-copy entries for ERROR_COPY coverage gate

The full-suite meta-test (src/shared/__tests__/error-copy.test.ts) requires a
user-facing ERROR_COPY entry for every literal 'ok: false, error: <code>' the SW
returns. The org handlers added org_not_configured (literal) with no copy → RED.
Add org_not_configured plus copy for the org codes that reach the popup via
thrown err.message (not_an_org_member, device_key_unavailable, not_in_org_context,
org_switch_failed). item_not_found already had an entry. (Dev-B added some of
these independently; B reconciles the wording when it syncs main post-merge.)

Full extension vitest: 70 files / 478 tests green (incl. error-copy 3/3).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014s527M917W47LDrfQ4t47g

extension/src/shared/error-copy.ts

@@ -113,6 +113,28 @@ export const ERROR_COPY: Record<string, ErrorCopy> = {
     title: 'Unsupported vault type',
     body: 'This vault uses a second-factor type not supported by this version of Relicario — update the extension.',
   },
+  // --- Org vault (Plan A) ---
+  org_not_configured: {
+    title: 'Organization not set up',
+    body: 'This organization is not configured in this extension yet — add it before switching to it.',
+  },
+  not_an_org_member: {
+    title: 'Not a member',
+    body: 'This device is not a member of that organization. Ask an org admin to add this device key.',
+  },
+  device_key_unavailable: {
+    title: 'Device key unavailable',
+    body: 'Unlock your personal vault first so this device can open organization vaults.',
+    cta: UNLOCK_CTA,
+  },
+  not_in_org_context: {
+    title: 'No organization selected',
+    body: 'Switch to an organization before viewing its items.',
+  },
+  org_switch_failed: {
+    title: 'Could not open organization',
+    body: 'Something went wrong opening that organization — check your connection and try again.',
+  },
 };
 
 export function lookupErrorCopy(code: string): ErrorCopy {